Is UFH worth the expense? Ooooooh, yes!!

[Tom]

I've been waxing some more beams in the house today and, as it's so cold, decided to fire up the under floor heating. Within half an hour you could feel the difference in the floor temperature and gradually the ambient temperature increased, too. I went outside after a while to have a break and do my stables and when I went back in it was absolute bliss!! Lovely warm feet and warm air all around. I'm soooooo glad we had it installed now If you're thinking about it and can afford it, just do it*


*Note, I'm not advocating anyone rip up their original Limecrete/brick/stone/whatever floor in order to do this!

 

[FamilyWiggs]

Since they took away our child benefit, we can't afford to turn ours on unless it gets to -5 oC !!

 

[Tom]

:shock:

 

[robgil]

is it expencive to run? ive often thought about ufh but my house is very draughty and uninsulated so i doubt it would be very effective , at the moment in some rooms when you look up at the ceiling you can see the floor boards of the room up above so if i did install ufh it would be working hard to heat not only the ground floor but the first floor as well.

 

[Tom]

I don't know how expensive it is, as we didn't really use it much last year. The most expensive bit will be getting the house warm. Then the floor and walls (ours are up to 3' thick) just act as a big storage heater. I believe electric UFH is very expensive but ours is a wet system run on natural gas by the Rayburn, which is on constantly anyway.

 

[FamilyWiggs]

Ours is nuclear*



(* electricity)

 

[Tom]

Would you be able to run it for a few days and monitor the consumption, to calculate a winter's bill? It might be lower than you think

 

[FamilyWiggs]

We ran it for about a month last year over Christmas. We had to sell one of the children and one of MIL's kidneys to pay the bill. :shock:

 

[Tom]

Yikes!!! :shock:

 

[Flyfisher]

The kidney sounds a bit much but at least you could have another child in time for next Christmas, so not too bad then. :wink:

 

[MdB]

Unless you are heating the ground by not having a good layer of insulation under the floor, I can't see that underfloor heating would be any more expensive to run than the equivalent system above the floor. Energy in = Energy out + losses. Put the same energy in with the same losses will give you the same energy out.

As for installation cost, ours was £900 on top of the cost of the floor itself for a wet system and was well worth doing. We are very happy with it and would fit it again if we were redoing the floor.

 

[robgil]

installation costs wouldn't bother me too much as id be putting it in my self , i would be more w2orried about it not being adequate at heating my old tea bag. The warm up period and its ability to do this as quickly as possible, in my view would be detrimental to its efficiency , so if its trying to create an ambient heat in a house that will not really allow this to happen in a reasonable time I.E. draughts and heat loss through walls and roof then perhaps a hotter system such as radiators would be better and more efficient?
keeping in mind a normal heating runs a lot hotter than UFH however UFH has a longer response time from cold.
So , my worry is that a colder system with longer response time would require a house with decent thermal efficiency to work correctly?

 

[Tom]

So , my worry is that a colder system with longer response time would require a house with decent thermal efficiency to work correctly?

Quite possibly, Rob, but remember that the heat from radiators goes up before it comes down so most of the heat is on the ceiling! With UFH, you feel the heat lower down and it cools as it goes up. From a comfort perspective, 'they' (whoever 'they' are) say this is what humans prefer; warmer feet and a cooler head. If you had UFH on a timer, all you'd do is adjust the times so it comes on earlier but goes off well before you go to bed. That way, the running times would be about the same as radiators.

However, I'm not an expert and I may be totally wrong!

 

[robgil]

how long is the response time on your system from absolute cold? Have you tried it in the dead of winter? and how well insulated is your house? , sorry to bombard you with questions.

 

[Tom]

Well, yesterday felt like the dead of winter to me and the floor was stone cold !! :lol: Within half an hour you could feel the change in the floor temp. The floor is LECA/Limecrete to current thermal regs, our walls are stone, up to 3' thick rubble infill and our ceilings are around 11' high. We have double glazing (aaarrghhhh!!!) but some of the windows don't shut properly...one is always 1" open :roll: The thermostats are set about 5' from the floor and the reading started to go up after about one hour. Hope this helps

 

[MdB]

Underfloor heating isn't ideal for houses that aren't fairly well insulated. There is a limit to the thermal output of the floor area for a given temperature and if you are losing a lot of heat the floor temperature may need to be too high to be comfortable for your feet.

Heat up time for the floor is slow and the more important heat up time for the room is slower still. In our house, it takes a day for the temperature to rise 5 degrees (from 15°C to 20°C) or so but then we only have the heat on for 10 hours whilst it is cheap. If it was on all the time, it would rise quicker. Quick response times and underfloor don't go together well as that isn't what they are designed for. However, if your house is well insulated, the temperature won't drop quickly removing this issue. I wouldn't want to put underfloor into a house without sorting out the overall insulation first.

 

[AMc]

We have underfloor and some radiators too. The problem with underfloor is the slow response time compared with radiators in well insulated rooms. The flow temp is lower and you have to warm the thermal mass of the floor before you start to feel the heat in the air. UF is very well suited to continuously occupied buildings, it is quite wasteful if you are only home in the evenings as you need to start warming it up a long time before you expect to use the room and it continues to release heat over several hours as it cools down below comfortable temperatures.
By contrast in a well insulated, draught proofed room radiators can raise the air temperature much faster, getting the room up to temp. in minutes.
A flip side of this is in my uninsulated solid walled rooms with rads the rooms themselves have slow response time because of the thermal mass of the walls - my power meter has a temp gauge and it showed that the rad part of my house took more than 2 hours to reach temp after the heat pump began to operate - so on a par with the UFH.

There is a very significant danger if you don't put enough pipe into a small room that you won't have surface to heat it adequately - as your room size gets bigger then permimeter heat loss gets less dramatic.
UFH is very dependant on the floor covering - in one room we had a wool rug over wood, removing it raised the temp. by 1C immediately. This was one of the few ways to actually improve the heat in that room as we're on a heatpump which is designed to produce low flow temps.

Heat travels by conduction (touching), convection (circulation of gas/liquid) and radiation (infrared light).
Radiators (hint in the name) don't just heat the air around them by convection which rises but emit radiant heat directly - which 'beams' across the room at you and feels warm more or less instantly.

How comfortable a room feels depends on a balance of the air movement in it, the temperature of any radiant heat sources as well as the actual air temperature.

If you are considering an underfloor heating system I would recommend you get a proper design done by an expert, the fitting is not complicated, but if you underspec it then bury the pipe in the floor you can't put it right.

As always money spent on reducing heat loss (fewer draughts and more insulation) will pay dividends in the cost and efficiency of any heating system.

If you want to know a bit more about thermal mass and heating systems The Green Building Bible contains some excellent material and isn't overly technical.

 

[robgil]

good info , thankis guys.
whats the greenh bibnle then?

 

[Penners]

The kidney sounds a bit much but at least you could have another child in time for next Christmas, so not too bad then.

Yes, keep the family production line running at full speed. Judging by yesterday's announcements you could need the income in the next few years.

Unfortunately, you only get one more kidney sale from MIL, so be sure to get the best price. Ebay perhaps?

 

[AMc]

good info , thankis guys.
whats the greenh bibnle then?

http://www.greenbuildingpress.co.uk/products.php?category_id=121
I bought both volumes and found them useful bey0ond the £17 cover price